1. Field of The Invention
The present invention generally relates to crawler cranes. Specifically, the present invention relates to crawler cranes with four crawler assemblies.
2. Discussion of Related Art
A crawler crane is a heavy duty machine which is used to lift, transport and place heavy loads, often exceeding 100 tons, from one place to another at a work site. As construction projects get more ambitious in scale, a need for crawler cranes that can lift, transport and place loads exceeding over 300 tons has developed.
An example of a crane that can lift over 300 tons is described in German Offenlegungsschrift 2 517 203 (xe2x80x9cthe ""203 German referencexe2x80x9d). In particular, the ""203 German reference describes a crawler crane that has four dual track crawler units. Each crawler unit is not directly connected to another crawler unit and is connected to the housing 8 via an outrigger. The tracks in each crawler unit are driven at different speeds and/or directions with respect to each other.
The crawler crane described in the ""203 German reference suffers from several disadvantages. For example, the assembly and disassembly of the crawler crane at a work site can be complex and time consuming. Similarly, the transport of the crawler crane from one job site to another can be difficult. The crawler crane also has limited mobility during movements performed irrespective of whether or not a load is being lifted by the crawler crane.
The described crawler crane suffers from several other disadvantages. For instance, it provides inadequate ground bearing pressures at the crawler assemblies for various forms of turning the crawler crane. The crawler crane described in the ""203 German reference also provides inadequate lifting characteristics by constraining its fulcrum points to be located over the centers of the crawler units.
The present invention regards a carbody and crawler assembly where the carbody includes a first beam with a first end and a second beam with a first end. A first crawler assembly is attached to the first end of the first beam and a second crawler assembly is attached to both the first crawler assembly and the first end of the second beam.
A second aspect of the present invention regards a crawler that includes a first crawler assembly and a second crawler assembly attached to the first crawler assembly, wherein the second crawler is aligned with the direction of travel of the first crawler assembly.
A third aspect of the present invention regards a method of assembling a first crawler assembly to a second crawler by positioning a first crawler assembly adjacent to a second crawler assembly and attaching the first crawler assembly to the second crawler assembly so that the first crawler assembly is aligned with the direction of travel of the second crawler assembly.
Each aspect of the present invention provides for a simpler design for a large load capacity crawler crane that reduces the complexity and time used to assemble, disassemble and transport the large load capacity crawler crane. Each aspect of the present invention also provides improved mobility for large load capacity crawler cranes during movements performed irrespective of whether or not a load is being lifted by the crawler crane.
Each aspect of the present invention also provides both adequate ground bearing pressures at the crawler assemblies used for turning the crawler crane. In addition, each aspect of the present invention provides adequate lifting characteristics by providing a larger fulcrum distance than other large load capacity crawler cranes, such as the crawler crane described in the ""203 German reference.
The foregoing features and advantages of the present invention will be further understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings, in which: